Use equal and member instead of eq and memq

Use equal and member instead of eq and memq

* lisp/cedet/semantic/complete.el (semantic-displayer-show-request):
* lisp/descr-text.el (describe-char-categories):
* lisp/mh-e/mh-identity.el (mh-select-identity):
* lisp/transient.el (transient--delay-post-command)
(transient--post-command):
* lisp/vc/vc-git.el (vc-git-create-tag):
* test/lisp/emacs-lisp/cl-lib-tests.el
(cl-lib-nth-value-test-multiple-values):
* lisp/emulation/viper-cmd.el (viper-preserve-cursor-color):
Use `equal` instead of `eq` and `member` instead of `memq` where
the comparison is with literals without guaranteed identity.
In some cases this change corrects evident bugs, in others it is
mostly cosmetic.